ATtiny261-ESSZ datasheet(123/227 Pages) ATMEL

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123

7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

The actual value from the port register will be visible on the port pin, when the Output Compare

Override Enable Bit is cleared. Table 16-20 shows the Output Compare Override Enable Bits

and their corresponding Output Compare pins.

16.11.6

TCNT1 – Timer/Counter1

This 8-bit register contains the value of Timer/Counter1.

The Timer/Counter1 is realized as a 10-bit up/down counter with read and write access. Due to

synchronization of the CPU, Timer/Counter1 data written into Timer/Counter1 is delayed by one

and half CPU clock cycles in synchronous mode and at most one CPU clock cycles for asyn-

chronous mode. When a 10-bit accuracy is preferred, special procedures must be followed for

accessing the 10-bit TCNT1 register via the 8-bit AVR data bus. These procedures are

described in section “Accessing 10-Bit Registers” on page 112. Alternatively the Timer/Counter1

can be used as an 8-bit Timer/Counter. Note that the Timer/Counter1 always starts counting up

after writing the TCNT1 register.

16.11.7

TC1H – Timer/Counter1 High Byte

The temporary Timer/Counter1 register is an 2-bit read/write register.

• Bits 7:2 - Res: Reserved Bits

These bits are reserved bits in the ATtiny261/461/861 and always reads as zero.

• Bits 1:0 - TC19, TC18: Two MSB bits of the 10-bit accesses

If 10-bit accuracy is used, the Timer/Counter1 High Byte Register (TC1H) is used for temporary

storing the MSB bits (TC19, TC18) of the 10-bit accesses. The same TC1H register is shared

between all 10-bit registers within the Timer/Counter1. Note that special procedures must be fol-

lowed when accessing the 10-bit TCNT1 register via the 8-bit AVR data bus. These procedures

are described in section “Accessing 10-Bit Registers” on page 112.

Table 16-20. Output Compare Override Enable Bits vs. Output Compare Pins

OC1OE0

OC1OE1

OC1OE2

OC1OE3

OC1OE4

OC1OE5

OC1A

(PB0)

OC1A

(PB1)

OC1B

(PB2)

OC1B

(PB3)

OC1D

(PB4)

OC1D

(PB5)

Bit

76543210

0x2E (0x4E)

MSB

LSB

TCNT1

Read/Write

R/W

Initial value

00000000

Bit

76543210

0x25 (0x45)

------

TC19

TC18

TC1H

Read/Write

RRRRRR

R/W

Initial value

00000000

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